1. Field of the Invention
The present general inventive concept relates to an image forming apparatus and a method to control a velocity ratio thereof, and more particularly, to an image forming apparatus which adaptively controls a velocity ratio of a developing device to a photoconductive medium according to an accumulation of a number of printed copies, and a method to control a velocity ratio thereof.
2. Description of the Related Art
An image forming apparatus using a two-component developer composed of a magnetic carrier and a non-magnetic toner develops an electrostatic latent image formed on a photoconductive medium with charged toner. In general, the image forming apparatus prints a fixed number of copies (for example, from 5,000 sheets to 50,000 sheets) using the two-component developer contained therein during a life cycle.
During their life cycles, the carrier, the toner, and the photoconductive medium used in forming an image are degraded, and consequently, there occurs deterioration of the image formed. Particularly, as more printing operations are performed, the less the carrier and the toner are charged. Also, a quantity of electric charge decreases as the number of printed copies increases, and thus, an optical density (OD) measured from an image printed on the paper increases, which deteriorates printing quality. This is because the OD is inversely proportional to the quantity of electric charge.
In order to remove a remainder of toner from the photoconductive medium, a cleaning blade is used. However, the cleaning blade causes abrasion on a film of the photoconductive medium. Accordingly, an amount of image developing increases, an amount of toner charging decreases, OD gradually darkens, and problems, such as blurring or scattering, become more severe. Herein, the scattering problem refers to toner that contaminates an inside portion of a printer engine rather than being used in developing the image on the photoconductive medium. As a result, an image quality of a conventional image forming apparatus deteriorates.